1. Field of the Invention
The present invention relates to a drive device using an electromechanical transducer, particularly to a drive device using an electromechanical transducer suitable for driving an X-Y moving stage for precision measurement, a picture taking lens for a camera, a projection lens for an overhead projector, a lens for a binocular or the like.
The present invention also relates to such apparatus as a measuring device, camera or the like equipped with a drive device using an electromechanical transducer.
2. Prior Art
When a drive pulse having a waveform comprising a gradual rise portion and a steep fall portion successive thereto is applied to a piezoelectric transducer, gradual elongation is caused in the thickness direction of the piezoelectric transducer at the gradual rise portion of the drive pulse and rapid contraction is caused at the steep fall portion. Hence, there is known a drive device in which by using this characteristic, charge and discharge are repeated at different speeds by applying a drive pulse having the above-described waveform to a piezoelectric transducer. A drive shaft member fixedly attached to the piezoelectric transducer is reciprocated at different speeds by generating an oscillation in the thickness direction having different speeds at the piezoelectric transducer, thereby moving a moving member frictionally coupled to the drive shaft member in a predetermined direction (refer to Japanese Laid Open Patent Publication No. JP-A-6-123830 as an example).
According to the above-described drive device using a piezoelectric transducer, when an environmental state such as temperature or humidity is changed after positioning a moving member, deformation is caused in a drive system, the moving member is shifted from a set position, and positional error is caused. For example, in the case of investigating how an inspection object is changed in response to environmental temperature, a sample table of a microscope is arranged in a hermetically sealed space, and inspection is carried out by changing the environmental temperature of the hermetically sealed space. In this case, when a drive device using a piezoelectric transducer is used in a device for moving the sample table, there causes inconvenience in the case of observing a change over time of the inspection object in which the sample table is moved by thermal deformation of the drive system caused by a change in the environmental temperature, and the position of the inspection object in the field of view of the microscope is shifted.